Dolphins stay awake 15 days

DOLPHINS can stay awake for 15 days or more by shutting down half their brain
at a time, scientists revealed yesterday.

The amazing trick allows the mammals to come to the surface when they need to
breathe — and to stay vigilant for sharks.

Researchers kept two bottlenose dolphin — a male called Nay and a female
called Say — hunting phantom “prey” over lengths of time that would have
left other animals sleep deprived and exhausted.

The creatures, which find food by sonar, were bombarded with man-made echoes
for five days at a time and found the targets with a success rate of up to
99 per cent. Say, who outperformed her male partner in San Diego,
California, was then tested for 15 days and her performance hardly faltered.

Scans confirm dolphins are capable of “unihemispheric sleep” — snoozing with
one side of the brain — while often keeping one eye open. Researcher Brian
Branstetter said: “These majestic beasts are true unwavering sentinels of
the sea.”